Desmacella cf. annexa (Schmidt, 1870)


Family : Desmacellidae

Form: Desmacella annexa Schmidt, 1870 is a massive or encrusting sponge with irregular, hispid surface. It has characteristic spiculation (microscopic examination). It has been dubiously recorded from Western Europe, mostly from deeper water. Massive or more encrusting, occasionally forming erect masses, with irregular hispid surface. Size may exceed 5 cm.

Colour: Beige, cream.

Consistency: Fragile, soft.

Surface: Often raised into irregular thickenings.

Apertures: Oscules with transparent rims at the centre of star-shaped excurrent channels.

Internal characters

Skeleton: Plumose, with ill-defined bundles and scattered single spicules generally directed towards the surface; no special ectosomal skeleton.

Spicules: Tylostyles with prominent tyles, quite variable in size: 220-1050 x 2.5-14 µm. Microscleres : Sigmas in two size classes: 25-42 and 11-15 µm; toxiform raphides, with a bend in the middle with a slight counter bend on both sides: 50-115 x 0.5-2 µm.

Habitat: Encrusting on other sponges, mostly in deep water but recorded from 5 m (Könnecker, 1973). Frequent on Stryphnus ponderosus at Rathlin Island.

Distribution: Roscoff, SW Ireland, Norway (Mediterranean, North Atlantic, Caribbean, Indian Ocean).

Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.

Identity: With experience this sponge can be recognised in situ but its existence at a particular locality would need to be confirmed by examination of the spicules in the first instance. This species was originally described from 350 m deep off the coast of Florida, with a tantalizingly short description. The assignment of European specimens to Schmidt's species is tentative and conspecificity with specimens from the Indian Ocean likewise needs further corroboration. It differs from the Western European D. inornata in the possession of the peculiar toxiform microscleres.

Editors: Christine Morrow, Bernard Picton & Rob van Soest.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland